A newspaper offset rotary printing press, referred to hereinafter as a rotary printing press, usually includes a plurality of producing units, called rotations, which can operate simultaneously and independently of one another (maximum 10). Each producing unit includes of reel stands for the paper rolls, draw rollers for feed and delivery of the paper web at the printing towers, printing stations which are combined as U printing groups (two printing stations), Y printing groups (three printing stations) or H printing groups (four printing stations) in one or more printing towers, auxiliary drives on the printing stations (e.g., for changing plates) and the folding unit.
A rotation is usually controlled by a plurality of programmable controller systems, which are in turn guided by higher-level control centers. To permit efficient data exchange, the systems are networked over serial bus systems.
A printing station includes a rubber cylinder, a plate cylinder and an inking and dampening unit. One ink color can be printed on one side with each printing station. A rotation includes all the printing stations which operate on one folding unit, i.e., all their printed paper webs are sent to one folding unit. The printing stations in a machine are accommodated in printing towers, a maximum of eight printing stations in one tower (eight-station tower). In the future, ten printing stations in one tower (ten-station tower) will be the goal. In one rotation, a maximum of twelve eight-station towers can work with one folding unit.
FIG. 1 shows a conventional rotary printing press with shafts. One, or in many cases even two mechanical longitudinal shafts 2 linked by gears 4 (e.g., conical gears) and mechanical vertical shafts 6 in printing towers 8, 10, 12 permit, due to rigid coupling, angular synchronization of all printing stations 14 with one another and with a folding unit 16 or 18 within one rotation. Synchronization is always necessary only within one rotation. Longitudinal shaft 2 runs through the entire machine and is usually driven by a plurality of main motors--for reasons pertaining to flexibility and torque distribution. Coupling and uncoupling of vertical shafts 6 and printing groups 20 take place by means of mechanical couplings 22. Furthermore, additional separating couplings 24 must be incorporated into longitudinal shaft 2 if individual printing towers 8 and/or 10 and/or 12 are to work in different rotations. By opening longitudinal shaft coupling 26 between printing tower 8 and printing tower 10, two rotations can operate independently of one another--printing tower 8 with folding unit 16 and printing towers 10 and 12 with folding unit 18.
The flexible allocation of printing stations 14 to a plurality of folding units 16 and 18 is determined exclusively by the mechanics. Any increase in flexibility must come at the price of an increased expense in terms of mechanical components (higher cost of acquisition of the machine).
Disadvantages of the conventional drive design with mechanical shafts include:
complicated and expensive mechanisms (gears, couplings), PA1 low flexibility in production, PA1 limited accuracy of printed images due to gear play, torsion of the shafts, manufacturing tolerances of the mechanical components, e.g., .+-.50 .mu.m in the print in newspaper rotations, PA1 tendency to vibration due to low mechanical natural frequencies, and PA1 high maintenance for the mechanical parts and for start-up of operation. PA1 greater flexibility (mixed production, target-group-oriented products), PA1 greater productivity (shorter set-up times, higher production speed, less waste), PA1 higher print quality (long-term constancy and greater accuracy &lt;.+-.20 .mu.m in the print), PA1 better economy (lower operating costs), and PA1 lower cost of acquisition of the machine. PA1 Straightforward design and simpler handling of the drive in synchronous operation (=the printing station is coupled and running in synchronization) and in isolated operation (=the printing station is uncoupled, e.g., for set-up work from an ongoing rotation). The drive can also be controlled, parameterized and diagnosed at any time without operating the synchronization bus. PA1 Only information ensuring angular synchronization of the drives in one rotation is transmitted over the synchronization bus. No control or parameterization data is transmitted. Thus, more than 100 drives in one rotation can be supplied with individual information at least once every two milliseconds.
For more than 30 years, there have been repeated attempts in the area of printing press development to replace the synchronization of the drive components by means of mechanical shafts with a synchro. This is done in conjunction with replacement of the d.c. technology with three-phase technology. In the 1960s and 1970s, several attempts were made in the development departments of printing press manufacturers Wifag, MAN Roland, in collaboration with electronics companies to introduce a drive technology without longitudinal shafts for gravure printing presses. However, this has not gone beyond the experimental stage in gravure printing technology. This research was not resumed until the beginning of the 1990s, this time in the area of rotary offset machines for newsprint. Hamada Printing Press Co. Ltd., the Japanese rotary (printing) machine manufacturer, developed a machine using only three-phase motors for each printing cylinder and each draw roller. The machine had no longitudinal shaft and no register rolls.
For the last several years, there has been increasing activity with regard to newspaper rotary presses in an attempt to replace the mechanical shafts, gear and couplings with a drive design having a single drive with synchronization via a synchro. ABB, in cooperation with Wifag, presented a rotary printing press without shafting at IFRA 94 in Munich. In this eight-station tower printing press, each printing station, each draw roller, and the folding unit were provided with a three-phase motor. All the longitudinal shafts and vertical shafts with conical gears and couplings were therefore eliminated, thus preventing most torsional vibration. The individual drive elements of a rotation are linked together only by a fast data line--a synchro. Synchro control is decentralized in the converter. Setpoints for the converter are selected and synchronized over a very fast serial field bus system. The SERCOS bus system is mainly used. This background information is described in an article entitled "Dem langswellenlosen Maschinenantrieb gingen viele Versuche voraus" Many Experiments Preceded the Longitudinal Shaftless Machine Drive), printed in the journal PRINT, Volume 39, 1994.
Newspaper rotary presses are trendsetters in the printing industry and are thus pioneers in the introduction of new drive designs. Technologies that prove successful in this field will also be introduced in other printing fields, such as gravure printing or printing of illustrations, packages, etc.
Trends in the printing industry include:
European Patent Application No. 0 567 741 describes a rotary printing press where the cylinders and at least one folding unit are driven directly. Several drives of the cylinders and their drive controllers are combined into printing station groups which can be allocated to one web of paper.
The printing station groups are connected to the folding unit and to an operating and data processing unit over a data bus. Within the printing station groups, the individual drives of the cylinders and their drive controllers are connected over a high-speed bus system. The printing station groups obtain their position difference directly from the folding unit. The higher-level control system is responsible only for selecting setpoints and deviations and for processing actual values. The higher-level control system is connected to a printing station group via the data bus, a drive system and a high-speed bus system. The positioning of individual drives relative to one another and to the folding unit is regulated in the drive system. In the drive system, data and commands coming from the higher-order control system are also adapted to the form needed for the drive controllers. Overall control over the data bus is limited to selection of setpoints, setpoint deviations, actual values, and setpoint control. Parameters for precision adjustment of the individual drives are calculated separately for each printing station group in the drive system.
With this rotary printing press, the printing station groups can be controlled only as a whole by one folding unit or another due to the fact that the entire control system is divided into a higher-order control system and autonomous printing station groups. However, it is impossible to integrate individual printing stations which are synchronized in one production with one folding unit into another production taking place in another rotation, synchronized with a second folding unit. Thus, the flexibility of this drive design is limited.